This invention relates to a fluid pumping system. More specifically, this invention relates to a fluid pumping system for pumping a fluid such as an hydraulic liquid, and having separate fluid outlet flows at different pressure levels.
Fluid pumping devices such as gear pump assemblies are readily available in the prior art. Such gear pumps typically comprise at least two meshing rotatable gears carried in a relatively close-fitting pump housing, with one of the gears being rotatably driven by a suitable motor. The housing includes a fluid inlet and a fluid outlet located on opposite sides of the gears generally along a common tangent between the meshing gears. As the gears rotate, a fluid is drawn into the fluid inlet, and is carried through the housing by the gears for discharge via the fluid outlet. From the outlet, the fluid is pumped further through conduits or the like to a desired location such as, for example, shaft bearings, control devices, etc. Of course, the pneumatic or hydraulic pressure of the fluid pumped through the conduits is related to the mass flow rate of the fluid and/or the particular load encountered.
Gear pumps are particularly useful in a wide variety of applications for supplying fluid such as lubricating oil to moving parts in many types of rotating machines. For example, in a typical gas turbine engine, a relatively high quantity of lubricant pumped at a relatively low pressure is required for the lubrication and cooling of bearings, transmission components, and the like. For such applications, gear pumps are convenient in that they are readily coupled to the rotating machine for rotation of the pumping gears along with the machine. However, with many machines such as a gas turbine engine, different quantities and pressure levels of fluid are required at different locations at varying intervals. For example, bearings and the like typically require relatively low pressure, high volumetric supplies of fluid whereas relatively high pressure low volumetric supplies of fluid may be intermittently required for operating control devices such as hydraulic controls and the like.
In the prior art, dual pressure fluid supplies have been obtained primarily through the use of separate gear pumps designed for supplying different fluid flow rates at different pressure levels. Alternately, prior art gear pumps have been provided including multiple pump stages, with output conduits being connected between pump stages for obtaining different output pressure levels. See, for example U.S. Pat. Nos. 2,256,743; 2,309,443; 2,699,726; 2,917,898; and 3,435,773 relating to the construction and operation of representative prior art gear pumps. All of these pumps are disadvantageous, however, in that they do not provide a minimum of pumping gears and pump control devices, and thereby do not minimize the cost and compactness of the pumping system. Moreover, these prior art pumping systems require relatively large amounts of machine power in order to provide a relatively high pressure fluid outlet flow.
This invention overcomes the problems and disadvantages of the prior art by providing a relatively compact and integrated fluid pumping system having a plurality of pumping gears and controlling valves cooperating to provide a plurality of fluid outlet flows at different flow rates and pressure levels, and requiring a minimum of power for operation.